Hithereto asbestos has been used as a reinforcement for an inorganic board, but environmental contamination due to the scattering of fine asbestos powder has become a serious problem, therefore, instead of asbestos, wood flake, wood fiber, and the like have been used as said reinforcement.
Nevertheless, the inorganic board in which said woody reinforcement is used has problems in that said inorganic board lacks mechanical strength and has poor freezing and fusion resistance.
To solve said problems, it is proposed that polyvinylalcohol be added to a mixture of said woody reinforcement and cement.
Said polyvinylalcohol acts as an adhesive in the inner structure of the inorganic board and prevents the drying of the surface of said inorganic board through its water holding property during curing in the autoclave and ensures uniform and smooth curing of the board in an autoclave, by making the water content of the papered sheet uniform.
Patent Literature 1U.S. Pat. No. 3,245,487Patent Literature 2Tokkaihei 6-329457Patent Literature 3Tokkaihei 5-124845